Discharge lamp apparatus



'Jan. 11, 1944. J. GATES Em. 2,339,051

DISCHARGE LAMP APPARATUS Filed April 8, 1942 Inventors:

' Julius Cates, Henry G. Jen kins, Sidney Noble, b W 6. J

y Their Attorpey.

able for continuous use.

- Patented Jam 11, 1944 Julius Cates, Wembley, Henry G. Jenkins, Pinner, and Sidney H. Noble, Harrow Weald, England; assignors to General Electric Company, a corporation of New-York I Application April 8, 1942, Serial Ne. 438 ,0534 In GreatBritain March 10, '1941 4 Claims. (Cl. 3 15100) Our invention relates to apparatus for starting and operating discharge lamps; Since such lamps have a negative temperature resistance coefiicient; it is necessary to employ a suitable ballasting impedance in series therewith. A form of such ballasting impedance commonly employed is a choke coil or reactorwhich functions not only to ballast the lamp but supplies avoltage surge by which the lamp is started. Where the .ballast employed is resistive, however, a starting voltage surge is lacking. One may of course add a reactor for the benefit ofstarting,

the lamp but the cost of it would be objectionable for, inasmuch as such a reactor would remain in the circuit during the operation of the capable of producing a desired inductive kick or voltage surge to efiectthe starting of the lamp.

. The reactor 5 normally is short-:circuited by 1 v the switch 1, that is, it is short circuited and lamp, it would-necessarily have to be a size'suit It is the object of our invention to provide an improved lamp circuit wherein even though the ballast is largely it not entirely resistive the lamp may be started by a voltage surge without the above mentioned objectionable cost.

In accordance with our invention we employ in the lamp circuit a. reactor of relatively light a andaccordingly inexpensive construction which while suitable for starting purposes would not be adapted for continuous use in the lamp circuit. 7

We provide a switch which normally short-circuits this reactor, that is, during the operation of the lamp but which is opened when the lamp is tobe started.

our invention" will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In. the single figure of the drawing which is a circuit diagram illustrating an embodiment of our invention i represents an electric discharge lamp, such for example as a fluorescent lamp, having therein the spaced thermionic electrodes 2. The lamp is connected to be supplied by alternating current from the source 3 which may be a 115 vol 60 cycle'lighting circuit. As shown the lamp is resistance ballasted, the ballast being represented byway of example as comprising the series connected incandescent lamp I which may be of common construction having a tungsten filament. Connected also in series with the lamp is the choke or reactor 5 and the control switch 6. The reactor 5 is of relatively light construc- -tion being lighter than that which would be required were it intended to be included in the path of the current supplied to the lamp during It may be salely employed in the its operation. lamp circuit, however, iorshort intervals and is hence inefiective during both the non-operation and the operation of the lamp. Although switches of various forms may be used we prefer and have illustrated the switch by way of example, as one of the thermal type having a bimetallic operating member. Inasmuch as the switch illustrated depends for its operation upon tem-- perature changes the controlling member? there for is shown as the heater awhich is arranged in good thermal relation therewith. The switch is self-biased when heated by its heater is deflected to an open -circuit position; hence, the switch may be defined as normally closed since that is its position when its actuating heater is not energized.

Moreover, that is its p'csition at all times except during a brief interval at each starting of the lamp. When the lamp is to be started the heater is energized to cause the switch to open thereby making the reactor available as a sourceof startstarting ing voltage.

For starting the lampone may use a switch of'any one of various well-known forms which connect across the lamp. Wehave chosen to show as a part of the present embodiment of our invention a glow discharge thermal starting switch. This switch -9 is connected in a series circuit with the heater 8 which circuit is bridged across the lamp. Where it is desired to preheat.

the lamp electrodes before applying the starting voltage the series circuit is connected to include them also as illustrated by the drawing. The

construction of the switch 9 is such that the waitage of the source applied to the lamp before it breaks down is suflicient to cause a glow discharge in the switch which by heating its then.

mal element causes the switch to close and thus short-circuit the glow discharge path. Because of the resulting cooling of the thermal element the switch then opens and presumably the lamp starts. After it has started the voltage across it is insuflicient to produce a glow in the starting switch; hence, the starting switch remains open. This switch may therefore be defined as a normally open switch since it is open when not energized and is in that position at all times except a very brief interval at each starting of the lamp. Inasmuch as the heater 8 is connected in scrim with the starting switch it becomes heated by the current flow therethrough to its closed circuit position butv voltage usually required. Soon after the lamp starts, the switch I will have cooled sufi'iciently to close the short circuit it provides about the reactor since the circuit of the heater 8 is maintained open by the starting switch.

If the ballast lamp 4 employed is such that it is fully loaded when the discharge lamp is operating it will be overloaded during the electrode preheating or lamp starting period. This condition we avoid by the insertion of a resistance, such for example as the small incandescent lamp [0, in the series circuit including the heater and the starting switch such that the ballast lamp will be only approximately fully loaded during the starting period.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination an electric discharge lamp having spaced thermionic electrodes, lamp ballasting means and reactive means connected in series with said lamp, 2, switch biased to closed circuit position for short-circuiting said reactive means, and a circuit connected across said lamp including means for opening said switch and a normally open starting switch for the lamp arranged in series, said starting switch serving to render said switch opening means ineffective after the lamp has started.

2. In combination an electric discharge lamp having spaced thermionic electrodes, a ballast resistor and a reactor connected in series with said lamp, a normally closed switch connected across said reactor, means for opening said switch, a normally open thermal starting switch and means connecting said means and said thermal switch in series across said lamp, whereby after said lamp has started said starting switch renders said switch opening means ineffective.

3. In combination an electric discharge lamp having spaced thermionic electrodes, a ballast resistor and a reactor connected in series with said lamp, a normally closed thermal switch connected across said reactor, a heater for said switch, a glow discharge lamp starting switch,

and means connecting said heater and said starting switch in series across said lamp.

4. In combination an electric discharge lamp having spaced thermionic electrodes constructed to be preheated by the flow of current therethrough, a ballast resistor and a reactor connected in series with the lamp, a normally closed thermal switch connected across said reactor, a

circuit connected across said lamp and in series with said electrodes, said circuit including a resistance heater in thermal relation with said thermal switch and a glow switch in series therewith for starting said lamp, said thermal switch having greater thermal inertia than said low switch.

JULIUS CATES. HENRY G. JENKINS. SIDNEY H. NOBLE. 

